This paper presents an innovative hybrid analytic-numerical approach to modelling species transport in fuel cells suitable for application on the system level. The core principle of this modelling approach is taking 1D numerical model for gas-flow and superimposing onto it a 2D analytic solution for concentration distribution in the plane perpendicular to the gas-flow together giving a 3D information on species concentration in the fuel cell. A hybrid analytic numerical model of a simple geometry isothermal fuel cell is presented and comparatively evaluated by benchmarking it against a professional full 3D CFD simulation tool. This evaluation shows very close agreement with the benchmarking 3D CFD simulation and computational times comparable to 1D models. This computational efficiency originates in the models analytic nature in the other two dimensions making it suitable for system level application. The paper features an extensive appendix with a comprehensive detailed mathematical derivation of the hybrid analytic-numerical model.
COBISS.SI-ID: 12841499
To augment the removal of pharmaceuticals different conventional and alternative wastewater treatment processes and their combinations were investigated. We tested the efficiency of two distinct laboratory scale biological processes: suspended activated sludge and attached-growth biomass, a combined hydrodynamic cavitation–hydrogen peroxide process and UV treatment. Five pharmaceuticals were chosen including ibuprofen, naproxen, ketoprofen, carbamazepine and diclofenac, and an active metabolite of the lipid regulating agent clofibric acid. To enhance the removal of pharmaceuticals hydrodynamic cavitation with hydrogen peroxide process was evaluated and optimal conditions for removal were established regarding the duration of cavitation, amount of added hydrogen peroxide and initial pressure, all of which influence the efficiency of the process. Optimal parameters resulted in removal efficiencies between 3–70%. Coupling the attached-growth biomass biological treatment, hydrodynamic cavitation/hydrogen peroxide process and UV treatment resulted in removal efficiencies of )90% for clofibric acid and )98% for carbamazepine and diclofenac, while the remaining compounds were reduced to levels below the LOD. For ibuprofen, naproxen, ketoprofen and diclofenac the highest contribution to overall removal was attributed to biological treatment, for clofibric acid UV treatment was the most efficient, while for carbamazepine hydrodynamic cavitation/hydrogen peroxide process and UV treatment were equally efficient.
COBISS.SI-ID: 26582055
The paper reports foremost the results of a successful combustion of an innovative lignocellulosic biofuel in a gas turbine. The fuel was processed through liquefaction of lignocellulosic materials with polyhydroxy alcohols in an acid catalyzed reaction. The liquefaction process features: high efficiency, high liquid yields and inexpensive, easily available process equipment. For the purpose of this analysis the following were developed: an experimental gas turbine with internal combustion chamber, a preheated pressurized fuel supply system with swirl-air fuel injector and a heat exchanger to obtain high primary air temperatures. The paper gives results on the emissions of CO, THC, NOx and soot. For the purpose of benchmarking the turbine was also run on diesel fuel. The paper presents analyses of the underlying phenomena with which it aims to provide guidelines for improvements in the fuel processing and in the experimental equipment. It has been shown that direct utilization of this innovative lignocellulosic biofuel gives promising results. Although the CO and THC emissions are higher compared to the benchmark diesel results it has been shown that both emissions decrease with increased turbine inlet temperature and with the increased fuel preheat temperature, due to a very high viscosity of the fuel. It is additionally shown that NOx emissions are low and comparable to those of the diesel fuel, whereas soot emissions are very low for both fuels.
COBISS.SI-ID: 12403483
The thermodynamic effects associated with the growth and collapse of a single cavitation bubble are investigated in the present paper by an experimental approach. The study focuses on the temperature variations in the liquid surrounding the bubble. Experiments are conducted in a cylinder partially filled with water at an ambient temperature and atmospheric pressure. The bubble growth results from the expansion of an initial air bubble, due to the pressure wave generated by a so-called tube-arrest method. Several locations of the bubble, at different distances from the bottom wall of the cylinder, are considered. The bottom wall is made of sapphire, which is transparent to both the visible and infrared light spectra which enables temperature measurements by a high-speed thermovision camera at a wavelength of 35 m. Water is opaque to the infrared light spectrum, hence only temperatures in the boundary layer and on the liquid vapour interface could be determined. A temperature decrease of 3 K was recorded during the bubble growth while an increase up to 4 K was detected during the collapse. Experimental results are compared to the predictions of the thermal delay model based on the assumption that the bubble growth and collapse are due to phase changes only. In this approach, the temperature variations are related to the latent heat exchanges during the vapourization and condensation processes. On the basis of these results, the respective effects of phase change and air dilatation/compression in the bubble dynamics are discussed.
COBISS.SI-ID: 13196827
In this paper we consider the optimal operating regulation of a self-sufficient energy network. To begin with we discuss the regulation of an optimised energy-supply system. Our task was initially focused on a theoretical description of the system-state matrix approach with a corresponding list of operating rules and actions. Secondly, a dynamic mathematical model consisting of the consumer, the energy-production facilities (a photovoltaic power plant and an internal combustion engine), the energy-saving capacities (a battery) and the regulation was set up. Thirdly, during the simulations with various regulation settings an optimised system of operating rules was set up to achieve a stable and rational supply of energy. Finally, the results, appropriate diagrams and guidelines for future work are presented.
COBISS.SI-ID: 12988187